This invention relates generally to deployable telescoping column structures employed in proposed Hoop-Column antennas and relates in particular to a latch securing mechanism for such columns.
In the continuous exploration and utilization of the spatial environment of Earth, the need for improved large structures is ever increasing. The size of orbital space structures is, at present, limited to the cargo volume of the National Aeronautics and Space Administration's Space Shuttle Vehicle. This vehicle has demonstrated the feasibility and practicality of transporting various payloads for deployment into spatial orbits about Earth. It has previously been demonstrated that folded, compressed, rolled and inflatable payloads may be compactly packaged for transport and expanded when placed in Earth orbit. This procedure has proved especially effective for weather and communication satellites, antennas and the like. Large volume structures which can be collapsed for storage and transport in relatively small volume and subsequently deployed at the site of use to envelop large volume and/or form planar, curved and contoured surfaces appear to have valuable future use in space, on Earth and/or on other planets.
Future spacecraft such as the hoop/column antenna are being designed as candidate Shuttle Transport System (STS) cargo. Antenna of this type are contemplated to be as large as 122 meters (400 feet) in diameter with the electronic feed system suspended on an 85 meter (279 foot) column when deployed. The antenna will be transported and stored within the STS cargo bay, deployed while the STS is in orbit and then re-stowed for STS transport back to Earth. One problem that has existed in previous deployment/re-stowing column or truss structures has been the inability of the structures to retain rigidity during operation while retaining re-stowing capability when it is desired to retrieve the structure for subsequent transport back to the original site.
Accordingly, it is an object of the present invention to provide an improved sequentially locking mechanism for telescoping column sections during column extension and reverse unlocking during column re-stowing.
Another object of the present invention is an improved securing mechanism for deployable telescoping column sections.
A further object of the present invention is an improved stress absorber and alignment system for the latching mechanism employed in deployable telescoping column sections.
An additional object of the present invention is an improved over-center latch for securing/releasing telescoping segments in a deployable/re-stowable column structure.
According to the present invention, the foregoing and additional objects are obtained by providing an improved column longeron latch as the securing mechanism for the deployable, telescoping column of the hoop-column antenna. The column is an open lattice, triangular structure with three longerons serving as the principal load bearing members and is divided into telescoping bays that are deployed after the antenna is placed in Earth orbit. The column longeron latch is a four-bar linkage mechanism using the over-center principle for automatically locking the longeron bays into position as deployed and serving to unlock the bays for re-stowing the antenna. The relative movement of the deploying longerons is under the influence of a cable-pulley-servo motor system with retrieval and re-stowing of the telescoped parts obtained by the same servo-motor pulling on a single cable threaded through the center of each column half and attached to the end column sections. The servo-motor is located within a center section of the column and the telescoping bays extend from opposite sides of this center section. In the illustrated embodiment, eleven internally nested telescoping bays are disposed on each of two opposite sides of the center section to give a total of twenty-three sections in the deployed column. Each nested bay or section of the column includes three longerons spaced 120.degree. apart, six diagonals and nine peripheral battens three of which are connected to each end and three intermediate of the longerons. A column longeron latch is located on each of the longerons to give a total of sixty-six latches for the entire column length. An opposite end housing of each longeron is provided with a cam-surface piston head to engage a rotatable bearing on the latch mechanism for the adjacent longeron. This piston is spring supported by a series of belleville spring washers that serve to absorb asymmetric load stress applied to the column.